An ambitious recombinant screening program was initiated under this project to detect I region variants, recombinants and mutants. To date, 1300 mice have been screened and four potential recombinants have been detected and are under characterization. These screenings are continuing under this project. In our continuing effort to characterize all the currently used H-2 haplotype strains we have now identified markers for the K and the D loci of the haplotypes H-2p and H-2r using new recombinants obtained from Dr. Jack Stimpfling. A third haplotype, H-2v, is currently being characterized. On completion we would have H-2 chromosomes which would be of considerable value in studies relating to immune response. Previously we were limited to only those few haplotypes where we had recombinants separating these loci. We have made considerable progress in identifying the silent alleles associated with the I-E subregion in certain haplotypes aspects of histocompatibility loci in general. We have extended the tissue cells and the eosinophils for expression of I region genes and products. Interesting findings have been made with the Peyer's Patch cells where Ia positive adherent cells are unable to present antigen. We have numerous collaborations going on the functional aspects of the I region genes with several laboratories which have already yielded some significant results. The two most interesting results which have come out in the past year have been the effect of genes in the H-2 gene complex on the infection to parasites and in susceptibility to autoimmune diseases such as myasthenia gravis and thyroiditis. These studies will be continued for further mapping of these genes.